An oath is a sworn statement, affirmation, or pledge, usually based upon religious principles and often used in legal matters. In a court of law, for example, all witnesses must swear that the testimony they give is the truth. Another example is the oath taken by public officials when they assume office. Members of the British parliament swear an oath of allegiance to the monarch - which Sinn Fein politicians elected in Northern Ireland have refused to do, thus causing them to be barred from sitting in the house. Aliens take an oath of allegiance when they become citizens of the USA. Taking an oath generally implies some legal or moral sanction for failing to carry out one' s sworn pledge; a trial witness, for instance, may be charged with perjury for lying under oath. The oath has its origins in religious customs, and some form of binding oath can be found in every culture.
Oaths are administered to those entering such institutions as the military, secret societies, religious orders, and marriage. Research Oath